Electric printing



Aug. 29, 1950 Filed Nov. 22, 1944 ZZQ W. J. HOOPER ELECTRIC PRINTING 4Sheets-Sheet l 9, 1950 w. J. HOOPER 2,520,504

ELECTRIC PRINTING Filed Nov. 22, 1944 4 Sheets-Sheet 2 II I l jzyaivzewAug. 29, 1950 w. J. HOOPER 2,520,504

ELECTRIC PRINTING Filed Nov. 22, 1944 4 Sheets-Sheet 3 1916 VOL 727655001? CE I 9, 1950 w. J. HOOPER 2,520,504

ELECTRIC PRINTING Filed Nov. 22, 1944 4 Sheets-Sheet 4 J97 6 VOL 73 7625jay/ T1: E

Patented Aug. 29, 1950 ELECTRIC PRINTING William J. Hooper, Elsah, Ill.,assignor, by memo assignments, to William O. Huebner, New York,

Application November 22,1944, Serial No. 564,574

18 Claims. (Cl. 101-426) This invention relates to electric printing,and more particularly to printing method and apparatus wherein the inkis transferred from an inked member to the sheet being printed by afield of force rather than by mechanical pressure.

One feature of this invention is that it provides improved methods andapparatus for electric printing; another feature of this invention isthat it is adapted to provide controlled uniform transfer of ink; stillanother feature of this invention is that the field across the air gapat which printing is taking place may be strong enough to have the airin such space at or above the ionization level; a further feature ofthis invention is that a relatively heavy electron space current iscaused to flow to assist in the movement of the ink; still a furtherfeature of this invention is that the flow of space current from eachincrement of area of the printing surface is controlled in such manneras to prevent formation of arcs; and yet a further feature of thisinvention is that each increment of area of the printing surface is, forall practical purposes, electrically isolated from adjacent areas and issupplied, prior to the instant of printing, with a. predetermined andcarefully controlled quanmy of electricity for effecting optimum resultsin the transfer of ink to the sheet being printed. Other features andadvantages of this invention will be apparent from the followingspecification and the drawings, in which:

Figure 1 is an elevational view, partly schematic, of one specificembodiment of my invention, an electric printing press of the kindwherein the sheet being printed is passed between two revolvingcylindrical members; Figure 2 is an enlarged detail view of the printinggap of the apparatus shown in Figure 1; Figure 3 is an enlargedfragmentary detail view analogous to Figure 2, but of a modified form ofapparatus; Figure 4 is a vertical sectional view, partly schematic ofanother modification of apparatus embodying my invention; and Figure 5is a vertical sectional view, partly schematic, of another modificationof apparatus embodying my invention.

Printing has for centuries been conventionally effected by mechanicalpressure between an inked member having a design thereon and the sheetto be printed. Very recently, however, it has been found that ink can betransferred from the inked member to the sheet being printed by the useof a field of force, either magnetic or electrostatic, without actualcontact between the inked member and the sheet. Certain arrangementsheretofore proposed for electric printing are shown in such patents asHuebner Patent 1,820,194 of August 25, 1931 and Huebner Patent2,224,39101 December 10, 1940, although these arrangements have nevergone into commercial use. A fulldiscussion of this type of printing willnot be set forth here, as reference may be made to the above mentionedpatents to supplement the present disclosure in regard to the advantagesbeing sought. It is believed sufficient to say that elimination of all.need for mechanical pressure enables very great reductions in the weightand power requirements of a large press, a goal toward which theprinting industry has been working for decades.

In view of the newness of electric printing, terminology peculiar tothis art has not as yet come into common use, and the words usedthroughout this specification and claims will be those employed in theconventional printing art wherein ink transfer is effected by mechanicalpressure. That is, for example, the term printing" is used to describethe operation of delivering ink from the inked member to the sheet beingprinted, although it will be understood that the word printing as usedherein does not connote any mechanical pressure, but is used in the muchbroader sense of the word to mean merely transfer of a certain designfrom one element to another. This is analogous to the use of the termprinting in photography, where mechanical pressure is not the cause oftransference of a design from the negative to the sensitized paper. Itwill be also understood that when one of the rolls or printing membersis spoken of as having designs formed on the surface thereof, suchdesigns may comprise text, pictures, or anything else desired to beprinted. Moreover, the designs may be formed on the surface of theprinting member in relief, by intaglio or gravure, or by planographic orlithographic methods. All such methods of forming or preparing aprinting surface are well known in the conventional printing art andneed not be described here, as is also the case in connection withmethods and apparatus for delivering ink to the inked surface in desiredquantities. In reading and interpreting this specification and theclaims accompanying it, all terminology borrowed from the conventionalprinting art must be given broad meaning appropriate to this ratherspecial field.

I have made a number of inventions in the field of electrical printing,these inventions being disclosed in certain copending applications towhich reference may be had, as applications Serial No. 567,605, filedDecember 11, 1944 (now abandoned); Serial No. 571,440, filed January 5,1945 (now abandoned); Serial No. 584,835, filed March 26, 1945; SerialNo. 590,704, filed April 27, 1945; Serial No. 604,618, filed July 12,1945; and Serial No. 617,186, filed September 19, 1945.

Referring now more particularly to specific apparatus illustrated inFigures 1 and 2 of the drawings, the press is here shown as comprisingupper and lower portions A and B suspended on a frame member or othercarrying means C. The lower portion includes .a main metal cylindricalmember or roll I having designs formed on the surface thereof, as textin relief. The cylinder I0 is mounted in conventional manner, notillustrated, to be rotatable about its axis II, and it is electricallygrounded throughout. The designs in relief on the surface of thecylinder I0 are inked by means here illustrated as conventional inkingmeans comprising the ink trough I2 and the rolls I3a-d. As will bereadily apparent to one familiar with the printing art, rotation of thecylinder I0 results in continually presenting to the printing point (inthis case the point directly above the axis of the cylinder) a surfacearea which has the desired quantity of ink on the raised portionsthereof and is devoid of ink on the other portions.

The upper portion of the press is here shown as including a housing I4having two cylindrical members or rolls I5 and I6 rotatable therewithinabout the axes I1 and I8, respectively, the axes II, I1 and I8 all beingparallel. All of the cylindrical members I0, I5 and I6 are driven from asingle drive means in synchronized relation and at such rotative speedsthat the lineal surface speeds are identical and so that adjacentsurfaces move in the same direction. The cylinders I0 and I6 may rotateclockwise and the cylinder I5 counter-clockwise, as indicated by arrowson the drawing.

At the bottom of the housing I4 are a pair of gap defining members I9and 20 of electrical resistance material having high specificresistivity and a relatively low dielectric constant, with high voltagebreakdown characteristics, as a high quality plate glass having adielectric constant of about four. These two members I9 and 20 are wedgeshaped, terminating in rather thin apices I'9a and 20a defining theprinting gap or air space in the form of a narrow strip extendinglongitudinally of the cylinders. That is, this gap might be in theneighborhood of an eighth to a half inch wide, and extend longitudinallyof the cylinders for their full length and parallel to their axes,preferably on a line between the axes II and I1; and the members I9and!!! operate to confine substantially the effective part of theelectric field of force in this gap. The adjacent or confrontingportions of the surfaces of the cylinders I0 and I5 are preferablyspaced a matter of a few hundredths of an inch at the printing gap, astwo hundredths of an inch. Too close a spacing is mechanicallyimpractical while too wide a spacing may result in loss of cleardefinition of the printed image due to dispersion of the inked designduring its transfer through space. The lower surfaces of the glassmembers I9 and 20 serve as bearingsurfaces over which pass the sheet tobe printed, a paper web 2| being illustrated as fed over the rolls22a-c; and these lower surfaces are preferably highly polished tominimize static electric effects incident to movement of the web over astationary bearing surface. To provide one factor of control inconnection with design clarity. ionization of the air at the printinggap, and other factors of operation of the press, it is desirable to beable to adjust the spacing between the electrical members II) and I5.This is shown as being accomplished by provision of a verticallyadjustable mounting for the entire upper printing section A. Thissection is here shown as supported from the frame C by bolts Ila-c. Thefirst two of these are mounted in slots, so that when they are loosenedthe housing It can be moved vertically through a desired range. The bolt23c is passed through a lug portion projecting from the frame C and isthreaded into a portion of the housing I4, that rotation of this bolt(and others like it at other portions of the support) enables raising orlowering of the upper section, the bolts 23a and 231) being tightenedduring operation of the press to maintain the selected position. A rangeof adjustment sufficient to enable the space between the cylinders IIIand I5 to be varied between limits of four or five thousandths of aninch and about fifty thousandths of an inch is desirable.

In the particular embodiment of my invention illustrated in Figures 1and 2, the cylindrical member I5 comprises an inner portion Iia ofconducting metal, as cast steel, and an outer surface portion I5b ofelectrical resistance material having high resistance to current flowtherethrough (high specific resistivity, at least ten to the tenth powerohms per cubic centimeter, and preferably ten to the nineteenth power orhigher), and a high specific inductive capacity or dielectric constant.The material illustrated is glass, which may have a dielectric constantin the neighborhood of ten, although it will be understood that othermaterials may be used which meet these qualifications even better, asfor example certain ceramics now being used in condensers and havingdielectric constants approaching 200, with a specific resistivity in theneighborhood of ten to the sixteenth power ohms per cubic centimeter. Itisdesirable that the material of the outer surface have very highresistance to current fiow'therealong, or therethrough (high specificresistivity), in order that the charge on any portion or increment ofsurface area will not rapidly move to another surface portion when thereare potential differentials therebetween, and will not rapidly leakthrough to the inner conducting metal portion which is grounded. A highdielectric constant is desirable to provide the maximum capacity effectwhen a quantity of electricity is being delivered to the surface, and toprevent breakdown or rupture of the material at the high voltages usedin this electric printing, which may be in the neighborhood of 10,000volts.

The upper cylindrical member or roll I6 also has an inner portion Iliaof electrically conducting-rigid material, as cast steel, but the outerportion I6b is in this case of electrically conducting but resilientmaterial. A material which I prefer in this regard is electricallyconductive rubber,

such material being readily available commercially. The spacing betweenthe axes of the cylindrical members I5 and I6 is preferably such thatthere is a definite compression of the surface of the rubber portion I6bwhere it contacts the outer glass surface of the roll I5, so thatcontact between these surfaces is provided throughout an area ratherthan as a line contact.

At the top of the upper portion of the press shown is a high voltagesource adapted to develop a relatively high direct current potentialbetween ground and its high voltage or "hot" output terminal, thisterminal being connected to the inner metal portion of the roll it, asindicated on the drawing. This high voltage source may be of aconventional type which can be secured on the commercial market, takingpower from an ordinary commercial alternating current source, as thewires 25 and 26, stepping its voltage up to the desired value, andrectifying and filtering this high voltage power. Manually variablemeans 21 enables convenient variation of the voltage developed, and theoutput voltage and current may be read from the meters 28 and 29,respectively. It is quite important that the voltage output be uniform,but this requisite is met by a piece of equipment commercially availablewhich will maintain any desired voltage gradient and deliver currentsmeeting the requirements of this invention. Voltage control apparatuscan be made for almost any power requirement. The current requirementsof this electric printing are not heavy in the ordinary sense of theword, but I have found that a very definite electron current or spacecurrent flow across the printing gap is requisite to good printing bythis method. An electron current of only one or two milliamperes fromeach square inch of printing area ma be all that is required, but wherethe roll is several feet in length, as in printing a newspaper web, thea total current flow in the high voltage circuit may approach theneighborhood of 100 milliamperes, even though the width of the printinggap is kept reasonably small.

In the operation of the device disclosed in Figures 1 and 2, the highvoltage source develops a potential with respect to ground and appliesthis to the conducting roll it. The electrically conducting surface ofthis roll contacts the high resistance and high dielectric constantsurface of the roll i5, resulting in the development of a high voltagedifferential between the surface of the roll ii, at the point ofcontact, and the inner metal portion ilia, which is grounded. There isthus a capacity or a condenser effect between the surface of the roll itand the inner electrically conducting portion IBa of the roll I5, sothat a certain quantity of electricity is delivered to the effectivecondenser provided by this contact. The capacity involved is a functionof the spacing between the metal portion Mia and the adjacent portion ofthe roll IS, the dielectric constant of the'outer portion Nb, and theareas involved. This effective capacity, the voltage delivered by thehigh voltage source, and the charging time, determine the quantity ofelectricity delivered to a given unit or increment of surface area ofthe roll 15 before it moves out of contact with the roll 16 during therelative rotation of these cooperating members; The primary variableshere, once the press has been constructed, are the rate of rotation andthe voltage, so that if a normal running speed is chosen the quantity ofelectricity delivered to a given unit of area of the outer surface ofthe roll l can be definitely predetermined by adjustment of the voltageby manipulation of the variable means 21.

Since the material of the outer portion of the roll I! provideshighresistance to current flow therealong or therethrough, the quantityof electricit 'delivered to any unit of area of the surface of the rolll5 remains unchanged, for all practical purposes, until that unit orincrement of area reaches the printing gap, since the high dielectricnature of the members it and 20 tend to prevent any transfer of chargebetween the cylinders Hi and I5 until the increment of area underconsideration reaches the air gap between these members is and 20. Whenthis point is reached, however, the spacing between the rolls I0 and I5should be small enough that there is an instantaneous and immediateelectron current or space current flow. I have found that it ispreferable to so connect the high voltage source that the surface of thecylinder is is given a high charge which is positive with respect toground. Accordingly, since the cylinder i0 is grounded, electron currentwill flow, at the instant of printing, from the uppermost surface of thecylinder I0 toward the cylinder I5. It is preferable not only to have adefinite space current or electron current flow as a part of thecausative effect of ink movement, but it is also highly desirabl to havethe electrons move from behind the ink in the sense that they leave themetal conducting surface of the cylinder l0 beneath the layer of ink onthe raised portions thereof, with the de-- sired direction of movementof ink articles or droplets coinciding with that of electron movement,as ink pigment particles such as colloidal graphite, for example, have anegative charge in the medium in which they are dispersed.

In order to get the maximum transfer of ink, and to improve uniformityand other desired characteristics in the ink image printed on the web2|, it is preferable to have the electron current at the printing gap ator above saturation or ionization conditions for electron currentmovement in air. As is well known, raising the voltage across an air gapcauses rapidly increasing electron current flow thereacross untilsaturation conditions are reached, whereupon substantial increases involtage effect little or no change in the electron or space currentflowing. If the voltage is increased further, however, a stage isreached where the electron current flow again begins to increase, thecurve of voltagecurrent curving up rather sharply and then increasingtremendously as there is an insulation breakdown and arcing occurs. Byprecise control of the quantity of electricity which can be delivered byany increment of area of the surfaces involved, the voltage conditionsacross the printing gap can be made high enough not only to work in thesaturation portion of the curve, but even to exceed this without dangerof arcing, since even though the voltage conditions are up in thecritical state there is not sufficient current punchavailable to resultin the formation of an arc. It will be readily appreciated, of course,that controlling the current output from the high voltage source wouldnot be sufflcient to achieve this result, if the surface of the roll l5were conducting, since development of arcing conditions at one pointcould result in the formation of an are, fed by electricity drawn fromother areas of the surface of the cylinder [5. Each increment of areainvolved in this electric printing must be printed independently, as itwere, if the conditions mentioned are to be obtained without disruptionof the operation by are formation. This control of current flow fromeach increment of area throughout the whole of the areas involved at theprinting gap is very important, and is achieved by an arrangement of thekind just described. By use of a cylinder like the cylinder IS, with,its outer portion of material having very high resistance to currentmovement and a high dielectric constant, and by proper adjustment ofspacing between the cyl- 7 inders It and ii and of the voltage deliveredby the high voltage source, the quantity of current on each increment ofarea given up at the instant of printing can be controlled so that theprinting gap is in a state of ionization, with a relatively substantialelectron current flow thereacross, yet without danger of arcing. It hasbeen found that arcing not only eventually damages the equipment, but itpiles up ink in an unrecognizable blob at and around the arcing pointand results in complete or substantially complete lack of ink transferat other points slightly further removed from the arcing point.

In the modified form of my invention shown in Figure 3 the paper web 33is in direct contact with the outer surface of a cylindrical member 34corresponding to the roll IS, in that this member 34 has an innercylindrical portion 34a of electrically conducting material such as caststeel, and an outer portion 34b of material having high resistance tocurrent fiow and a high dielectric constant for capacitive purposes, asglass or a special ceramic. In this case the sheet to be printed, as theweb 33, is in contact with the outer surface of the cylindrical member34 at the printing point closest to the cooperating cylindrical member35. This latter member is of electrically conducting material, as caststeel, with designs formed on the surface thereof, as by putting a platewith relief designs thereon, and is appropriately inked by anyconventional method. In the form of-my invention shown in Figures 1 and2, transfer of ink is limited to a definite and physically definedprinting gap, with the space across this gap such that the capacity atthe gap between the members Ill and lint is less than that between themembers lid and it during the charging period, so that the strain orvoltage gradient at the gap is higher than that during charging contactbetween the rolls l and it. In the modification shown in Figure 3 thisincrease in voltage strain at the printing portion of revolution alsotakes place, but no attemptis made to define printing to a narrow arc Ofrotation, although as a practical matter the strain between the membersis not such as to efiect transfer of ink except where the cylinders areclosest, although printing may take place over an inch or more of widthat and-about this point of closest spacing. Although it is desirable tofeed the web of paper 2| in the printing arrangement shown in Figures 1and 2 at a lineal speed corresponding to the lineal surface speeds ofthe rolls ill and I5, physical contact in the first form took placebetween the moving web and stationary members. In the form shown inFigure 3, however, use of the same lineal speeds enables the paper to beguided.

or carried directly by the surface of the roll 34 at the printing point,with no relative rotation therebetween, so that there is no chance ofinterference by static electricity transients if a static eliminator hasbeen used in conjunction with the web prior to the printing points.

In the embodiments of my invention illustrated in Figures 4 and 5 thedesired quantity of electricity is delivered to the outer surface of theprinting roll by controlled conduction through the roll, rather than bycontact ofthe surface with a conducting member, as the conducting rollit. In this case the outer portion of the high voltage roll must be ofmaterial having what might be termed only moderately high resistance tocurrent flow, (as for example ten to the seventh or eighth power ohmsper cubic centimeter) so that the desired quantit of current can flow toa given increment of area, through the roll, be-' time the electricalresistance is high enough to prevent any appreciable transfer ofelectricity between adjacent increments of area at the instant ofprinting to prevent formation of arcs.

Referring now more particularly to the embodiment illustrated in Figure4. a cylindrical member 40 rotates within a. metalhousing 4| having agenerally cylindrical inner surface. A pair of members 42 and 43 ofmaterial having a high specific resistivity and a relatively lowdielectric constant and corresponding to the members II and 2| describedin connection with Figures 1 and 2, define the printing gap and provideguide means for the paper web 44 traveling over the rolls 450-0. Ink isdelivered from a fountain trough 43, through an intermediate roll 41, toa smooth inked roll 48, the roll 4! serving to ensure uniformdistribution of the ink on the roll 48. The roll 43 is of electricallyconducting material throughout, preferably comprising a cast metal innerportion and an outer blanket portion of conducting rubber, although throll may be entirely of metal.

In this case the designs are shown as formed in relief on the exteriorsurface of the high voltage roll 40. By having the relief portionsubstantially raised above the remainder of the surface of this roll,and by properly adjusting the spacing between the rolls 40 and 43, inktransfer from the roll 48 to the web 44 will take place at the printinggap only in accordance with the configuration of the raised-portions ofthe surface of the roll 40. That is, the field strength between theraised portions of the surface of the roll 40 and the surface of theroll 48 is so much greater than that existing with respect 'to the loweror unraised portions of the surface that the desired ink transfer takesplace in the designs determined by the raised portions without anynoticeable ink transfer taking place elsewhere. One advantage of thisarrangement is that all wear and tear on the surface bearing the design,even that incident to repeated reinking, is eliminated. As in all formsof printing apparatus shown in this application, the web 44 is spacedfrom the inked surface of the roll '48 at the printing point.

The inner portion 40a of the roll 40 is of electrically conductingmaterial, as cast steel, connected to the hot terminal of the highvoltage source indicated schematically, which may be like that describedin connection with Figure l. The outer portion 40b of this roll is ofmaterial of fairly high resistance, but not high enough to preventappreciable current flow therethrough during the time of one revolutionof the roll. Certain waxes, as red sealing wax, can be used for with theouter surface of the inner metal portion 40a. In order to build up thedesired charge of electricity on the outer surface of the roll 40, thehousing 4| is arranged to have a condenser action in cooperation withthe inner metal portion 40a of the high voltage roll, and to increasethe effect of this action the interior of the housing-ll is providedwith an inner lining or portion 4 Id of material having a highdielectric constant, as glass. Throughout about of its circumference,therefore, there is a capacity relation between th portion 40a and theouter metal portion of the housing ll, providing a condenser which ischarged by the high voltage source and discharged at the instant ofprinting, in so far as any given increment of surface area is concerned.The resistance in ohms at any given section through the outer portion40b of the high voltage cylinder must be so proportioned that, at thevoltage at which the arrangement is being operated, the desired quantityof electricity i delivered to the outer surface during rotation of agiven increment of area after it has effected printing and until itagain reaches the printing point. This may be determined in accordancewith the conventional charging time formula where the time constantt=RC, where t is in seconds, R in ohms and C in farads. The resistanceand capacity of a given incremental section through the outer portion40b ar fixed in the design and construction of the press. and arepreferably so proportioned in relation to the time provided at thedesired normal running speed that about two-thirds or three-quarters ofthe eventual maximum charge which could be delivered to an increment ofsurface area if the roll is stationary is delivered to it during thecharging portion of one revolution. As before, adjustment of the spacebetween the rolls 40 and 48, and

adjustment of the voltage delivered by the high.

voltage source, enable the printing gap to be operated at or above theionization level, yet with control of the current flow such that noarcing takes place.

The form of my invention illustrated in Figure is another form orembodiment of my invention of charging the surface of the high voltageroll, in electric printing, by controlled conduction through the roll.In this form of my invention the roll 50 has an inner portion 50a ofconducting material, as cast steel, and an outer portion of moderatelyhigh resistance material highly resistant to an electrical breakdown, asglass with a metal salt dispersed therethrough, this outer portion beingidentified as 5%. An outer metal housing 5| provides an innercylindrical surface again providing a capacity relationship with theportion 50a, the housing being provided with a lining here identified as5la, which may be of polystyrene or glass, for example, having arelativelyhigh dielectric constant. Glass members 52 and 53 again serveto define the printing gap and to act as guides for the web 54 movingover the rolls 55a and 55b. As before, the outer surface of the roll 50is charged from the high voltage source by conduction through the roll,as described in connection with the embodiment of my invention shown inFigure 4.

The design to be printed is in this case formed on the outer surface ofthe lower rotatable cylinder 58, this cylinder being of conductingmaterial, as a cast steel inner portion with metal type plates thereon,and grounded. Ink in a trough 56 is delivered through the intermediateroll 5] to inking rolls 59a and 59b to continually replenish ink takenfrom the roll 58 during the printing operation. The operation of thisform of press is similar to that more fully described in Figure 4,except that ink is present only on 10 the portions corresponding to thedesign to be printed, at the printing point.

While I have shown and described certain embodiments of my invention, itis to be understood that it is capable of many modifications. Changes,therefore, in the construction and arrangement may be made withoutdeparting from the spirit and scope of the invention as disclosed in theappended claims.

I claim:

1. Transfer apparatus of the character described, including: a rotatingcylindrical member having at least the surface thereof of electricalresistance materialhaving high voltage breakdown characteristics, eachincrement of area of said member being adapted to retain a quantity ofelectricity; a source of liquid to be transferred; a sheet spacedtherefrom; means for developing a potential differential between saidmember and sheet; andmeans for delivering a predetermined quantity ofelectricity to each separate increment of area of the cylindrical memberprior to its reaching the transfer zone.

2. Printing apparatus of the character described, including: a firstmember; a second member spaced from the first member, one of saidmembers having designs formed on the surface thereof and one of saidmembers having the surface thereof and a substantial portiontherebeneath of electrical resistance material having a high dielectricconstant; means for inking one of said members; means for supporting thesheet to be printed between said members and spaced from the inkedmember; and means for supplying said resistance surface with anelectrical charge of predetermined quantity and having a high voltagedifferential from said other member.

3. Printing apparatus of the character described, inciuding: a firstcylindrical member; a second cylindrical member spaced from the firstmember, the axes of said members being parallel, one of said membershaving designs formed on the surface thereof and one of said membershaving the surface thereof and a substantial portion therebeneath ofelectrical resistance material having a high dielectric constant; meansfor inking one of said members; means for supporting the sheet to beprinted between said members and spaced from the inked member; and meansfor supplying said resistance surface with an electrical charge ofpredetermined quantity and having a high voltage differential from saidother member, the inked member being negative with respect to the othermember.

4. Printing apparatus of the character described, including: a firstcylindrical'member; a

second cylindrical member spaced from the first member, the axes of saidmembers being parallel, one of said members having designs formed on thesurface thereof and one of said members having the surface thereof and asubstantial portion therebeneath of high resistance material having ahigh dielectric constant; means for adjusting the spacing between saidmembers; means for inking one of said members; means for supporting thesheet to be printed between said members and spaced from the inkedmember; and means comprising a power supply for supplying said highresistance surface with an electrical charge of predetermined quantityand having a high voltage differential from said other member, the inkedmember being negative with r p qi t9 the other member, this power p lymeans being variable to enable the space between said members to bemaintained at or above the ionization level.

5. Printing apparatus of the character described, including: a firstmember; a, second member spaced from the first member, one of saidmembers having designs formed on the surface thereof and one of saidmembers having the surface thereof and a substantial portiontherebeneath of high resistance material having a high dielectricconstant; means for inking one of said members; means for supporting thesheet to be printed between said members and spaced from the inkedmember; and means for supplying said high resistance surface with anelectrical charge of predetermined quantity and having a high voltagedifierential from said other member, this means including a conductingmember making moving contact with said high resistance surface.

6. Printing apparatus of the character described, including: a firstcylindrical member; a second cylindrical member spaced from the firstmember, the axes of said members being parallel, one of said membershaving designs formed on the surface thereof and one of said membershaving the surface thereof and a substantial portion therebeneath ofhigh resistance material having a high dielectric constant; means forinking one of said members; means for supporting the sheet to be printedbetween said members and spaced from the inked member; means forrotating said cylindrical members and moving said sheet, this meansproviding equal surface speeds, in the same direction, of the sheet andat least one of the cylindrical members; and means for supplying saidhigh resistance surface with an electrical charge of predeterminedquantity and having a high voltage differential from said other member,this means including a conducting member making moving contact with saidhigh resistance surface.

7. Printing apparatus of the character described, including: a firstcylindrical member; a second cylindrical member spaced from the firstmember, the axes of said members being parallel, one of said membershaving designs formed on the surface thereof and one of said membershaving the surface thereof and a substantial portion therebeneath ofhigh resistance material having a high dielectric constant; means forinking one of said members; means for supporting the sheet to be printedbetween said members and spaced from the inked member; means forrotating said cylindrical members and moving said sheet, this meansproviding equal surface speeds of said members and sheet in the samedirection; and means for supplying said high resistance surface with anelectrical charge of predetermined quantity and having a high voltagedifferential from said other member, this means including a cylindricalmember of resilient material of good electrical conductivity makingcontact with said high resistance surface circumferentially remote fromsaid sheet.

8. Printing apparatus of the character described, including; a firstcylindrical member having the surface thereof and a substantial portiontherebeneath of high resistance material having a high dielectricconstant; a second cylindrical member of material of good electricalconductivity having designs formed on the surface thereof, the axes ofsaid cylindrical members being parallel and the adjacent surfaces beingslightly spaced; means for inking said second member; means forsupporting the she t to be printed between said members and spaced fromthe inked member; and power supply means for supplying said highresistance surface with an electrical charge of predetermined quantityand having a high voltage differential from said other member, the inkedmember being negative with respect to the other member, this powersupply means being variable to enable the space between said members tobe maintained at or above the ionization level.

9. Printing apparatus of the character described, including: a firstcylindrical member having the surface thereof and a substantial portiontherebeneath of high resistance material having a high dielectric factorand an inner portion of material of good electrical conductivity; asecond cylindrical member spaced from the first member, the axes of saidmembers being parallel, one of said members having designs formed on thesurface thereof and one of said members having the surface thereof and asubstantial portion therebeneath of high resistance material having ahigh dielectric constant; means for inking one of said members; meansfor supporting the sheet to be printed between said members and spacedfrom the inked member; means for rotating said cylindrical members andmoving said sheet, this means providing equal surface speeds of saidmembers and sheet in the same direction; and means for supplying saidhigh resistance surface with an electrical charge of predeterminedquantity and having a high voltage differential from said other member,this means including a cylindrical member of resilient material ofgoodelectrical conductivity making contact with said high resistancesurface circumferentially remote from said sheet, the inner portion ofthe first cylindrical member being at the same potential as said secondcylindrical member.

10. Printing apparatus of the character described, including: a firstcylindrical member having the surface thereof and a substantial portiontherebeneath of material having a high dielectric constant; a secondcylindrical member of material of good electrical conductivity havingdesigns formed on the surface thereof, the axes of said cylindricalmembers being parallel and the adjacent surfaces being slightly spaced;means for inking said second member; means for supporting the sheet tobe printed between said members and in contact with a portion of thefirst cylindrical member; and means for supplying the surface of one ofthe members with an electrical charge having a high voltage differentialfrom said other member.

11. Printing apparatus of the character described, including: a firstcylindrical member having the surface thereof and a substantial portiontherebeneath of electrical resistance material having a high dielectricconstant; a second cylindrical member of material of good electricalconductivity having designs formed on the to enable the space betweensaid members to be maintained at or above the ionization level.

12. Printing apparatus of the character described, including: a firstmember; a second member spaced from the first member, one of saidmembers having designs formed on the surface thereof and one of saidmembers having the surface thereof and a substantial portiontherebeneath of high resistance material having a high dielectricconstant; means for inking one of said members; means for supporting thesheet to be printed between said members and spaced from the inkedmember; and means for supplying said high resistance surface with anelectrical charge of predetermined quantity and having a high voltagedifferential from said other member, this means including a conductingmember in good capacitive relationship with the member having the highresistance surface.

13. Printing apparatus of the character described, including: a firstcylindrical member; a second cylindrical member spaced from the firstmember, the axes of said members being parallel, one of said membershaving designs formed on the surface thereof and on of said membershaving the surface thereof and a substantial portion therebeneath ofhigh resistance material having a high dielectric constant; means forinking one of said members; means for supporting the sheet to be printedbetween said members and spaced from the inked member; and means forsupplying said high resistance surface with an electrical charge ofpredetermined quantity and having a high voltage differential from saidother member, the inked member being negative with respect to the othermember, this means including a conducting member at least partlysurrounding and in good capacitive relationship with the cylindricalmember having the high resistance surface.

14. Printing apparatus of the character described, including: a firstcylindrical member; a second cylindrical member spaced from the firstmember, the axes of said members being parallel, one of said membershaving designs formed on the surface thereof and one of said membershaving the surface thereof and a substantial portion therebeneath ofhigh resistance material having a high dielectric constant; means forinking one of said members; means for supporting the sheet to be printedbetween said members and spaced from the inked member; and means forsupplying said high resistance surface with an electrical charge ofpredetermined quantity and having a high voltage differential from saidother member, the inked member being negative with respect to the othermember, this means including capacity means at least partly surroundingand in good capacitive relationship with the cylindrical member havingthe high resistance surface, this capacity means having an inner portionof material having a high dielectric constant and an outer portion ofconducting material at the same potential as the other cylindricalmember.

15. A method of printing by use of two spaced members, at least one ofthe members being a rotating cylindrical member having a surface of highresistance material having a, high dielectrio constant, one of themembers having designs formed on the surface thereof and one of themembers providing a source of ink for transfer to a sheet to be printed,comprising: supporting the sheet to be printed between said members andspaced from the ink; and developing a potential differential betweensaid members and controlling the current flow between said members atthe instant of printing by bringing each increment of area of thecylindrical member in contact with a charged conducting member prior tothe instant of printing by such increment of area to deliver apredetermined quantity of electricity thereto.

16. A rotary capacitor comprising a cylindrical member having an innercylindrical plate portion of electrically conducting material and anouter surface dielectric portion of material having a high dielectricconstant.

17. Current controlling apparatus, including: a rotary capacitor havingat least a surface portion of material having a high dielectricconstant; means associated with said capacitor for charging incrementsof area of said surface portion as they come in operative relationthereto; and means associated with said capacitor for dischargingcharged increments of area of said surfac portion as they come inoperative relation to this latter means.

18. Apparatus of the character described for controlling high voltage,low amperage current flow throughout a substantial area, including: arotary capacitor comprising a cylindrical member having an innercylindrical portion of electrically conducting material and an outersurface portion of material having a high dielectric constant; meansassociated with said capacitor for charging increments of area of saidsurface portion as they come in operative relation thereto; and meansassociated with said capacitor for discharging charged increments ofarea of said surface portion as they come in operative relation to thislatter means.

WILLIAM J. HOOPER.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,600,842 Philips Sept. 21, 19261,820,194 Huebner Aug. 25, 1931 1,838,218 Durham Dec. 29, 1931 2,042,003Huebner May 26, 1936 2,065,136 Huebner Dec. 22, 1936 2,152,077 MestonMar. 28, 1939 2,173,032 Wintermute Sept. 12, 1939 2,224,391 Huebner Dec.10, 1940 2,451,288 Huebner Oct. 12 1948 FOREIGN PATENTS Number CountryDate 301,508 Germany Feb. 2, 1917 176,469 Switzerland June 17, 1935

